Teledyne LeCroy DA1855A - Manual (Page 30)

DA1855A Differential Amplifier
24 922258-00 Rev A
Power Connection
Check to make sure the power switch located on the rear panel is in the OFF position. Connect the
power cable to an appropriate power source. The DA1855A will operate on a 50 or 60 Hz AC power
source with a nominal voltage range from 100 V to 240 V.
Comparator Mode
The DA1855 becomes a differential comparator when the internal Precision Voltage generator (PVG)
output is selected as the amplifier’s inverting (–) input. The – Input is disconnected form the
amplifier and does not serve any purpose in the V
COMP
mode. In this mode the DA1855A can be used
to very accurately measure relatively small signals riding on large DC components.
Figure 1, Block Diagram V
COMP
Mode
Differential Mode
The DA1855A built-in Precision Voltage Generator can be used to generate a true differential offset
while still allowing both inputs to be used as differential inputs. This mode facilitates making
measurements such as changes to a transistor’s base to emitter voltage caused by variations in
temperature. Used in this mode, the voltage generator can be set to a value that will zero out the
static value of the junction’s ON voltage. the DA1855A’s differential measurement capability will
reject any dynamic signal common to both sides of the junction and the oscilloscope is left to
measure only the changes in the junction voltage.